Why would you throw away your eggshells when they’re so useful?
There are a myriad of ways to recycle them. My favourite is for soil improvement.
Years ago, I came across a gardening tip for reusing eggshells. Until recently, I hadn’t given it a try.
The accepted wisdom seems to be that crushing discarded eggshells and digging them into the garden or adding them to your compost is an effective way to add minerals, especially calcium, to the soil. The shell of a chicken egg is comprised of about 96% calcium carbonate (CaCO3) crystals which are bound together by proteins. Calcium is essential for building strong plant-cell walls, enabling vigorous and rapid plant growth. Without it, plants like tomatoes, capsicums and squash for example, are likely to develop blossom-end rot, resulting in a failed crop.
Some advice is that crushed eggshells can deter pests like caterpillars, slugs and snails, which suffer a thousand tiny cuts when they crawl across the grit causing dehydration and eventual death – sounds gruesome! I can’t attest to this because I use my crushed eggshells in a more indirect way.
My compost worms love them!
I’ve written in the past about my worm farm and how vital the ‘worm tea’ and castings it produces are for soil health. Besides which, it’s a great recycling tool for eating up my kitchen waste, as well as old paper and cardboard.
I discovered that calcium provided by the eggshells, reduces high acid conditions in the worm farm which is detrimental to the worms and can make the farm smelly as well. Crushed eggshells also provide grit to aid the worms’ digestion. ‘And, it is believed that eggshells help worms in the reproductive process’ (ref). I have yet to verify this but since they are such prolific little critters, I’m not about to argue.
If you intend trying this on your worms, take care to crush the shells to a very fine grit. I use a mortar and pestle to grind them down. Since composting worms don’t have teeth, the grit must be small enough for them to swallow; apparently they need a bit of grit to help digest the food scraps.
It’s also important not to overdo adding eggshells to your farm. About a half cup of grit at a time is sufficient for most household worm farms to manage. Don’t add more until the previous batch is no longer visible. Any surplus I have is added to my citrus which seem to appreciate the extra dose of calcium.
I was a little concerned about using eggshells because of the possibility of introducing salmonella into the worm castings. Many sites advocate the washing or heating of eggshells before introducing them to the worm farm of compost. I do neither. But I am careful to wash my hands after gardening. The Michigan State University report is reassuring: ‘Egg shells are often such a small percentage of the whole, that rarely are they able to overwhelm a batch of compost. Overall, after the composting process is finished and cured, most pathogens will be brought to a similar level as the surrounding soil thus reducing the amount of salmonella bacteria in your compost.’
One of the most encouraging things I found while researching the benefits of egg shell to the soil, was how it’s been demonstrated (in a calcined form) to ‘mitigate the accumulation of antibiotics, heavy metals, antibiotic-resistant bacteria (ARB)/antibiotic resistance genes (ARGs) in vegetables [which] has become a new threat to human health’ (ref). In the study referenced, adding the modified egg shells to the soil of a growing bell pepper, impeded the uptake of pollutants like those mentioned above.
I can’t help thinking the answers to many of our pollution questions lie in nature herself. The microbes found to disseminate oil spills also comes to mind (ref).
“The human race is challenged more than ever before to demonstrate our mastery, not over nature but of ourselves.”
― Rachel Carson